To: linux-kernel@vger.kernel.org
From: Stephen Hemminger <shemminger@osdl.org>
Subject: Re: Connection reset by peer - TCP window size oddity ?
Date: Mon, 3 Oct 2005 10:16:11 -0700
Organization: OSDL
Message-ID: <20051003101611.43714e53@dxpl.pdx.osdl.net>
References: <Pine.GSO.4.61.0510031241580.29231@scorpio.gold.ac.uk>
	<87r7b2k6de.fsf@newton.gmurray.org.uk>
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On Mon, 03 Oct 2005 15:44:13 +0100
Graham Murray <graham@gmurray.org.uk> wrote:

> Martin Drallew <m.drallew@fatsquirrel.org> writes:
> 
> > A tcpdump follows and, unless I'm misunderstanding the output (quite
> > possible) it looks like the kernel is sending outside of the peer's
> > TCP window, to which the peer responds by resetting the connection.
> 
> I think that you have overlooked one detail in the output. Both
> systems have declared window scaling of 2, so when otter sets the
> window size of 1984 in the packet it is actually advertising a window
> of 7936, which you are not exceeding. You do not say what type of
> system otter is (or what OS it is running), so one explanation is that
> otter has just mirrored your 'wscale 2' in its SYN-ACK without
> actually meaning it.

So you have a firewall in between the systems? There have been firewall's
that strip off the window size option, and this causes all sorts of
nasty problems like this.

-- 
Stephen Hemminger <shemminger@osdl.org>
OSDL http://developer.osdl.org/~shemminger
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